Installing Bathroom Vanity on Uneven Concrete Floor

Bathroom Vanity Installation Solutions for Dealing with a Sloped Concrete Floor

By Mark J. Donovan

Question: I read your article on installing a bathroom vanity that included information on leveling a vanity. Unfortunately I don’t think it is going to work for my particular vanity situation.

I am installing a bathroom vanity on a different wall than the old vanity in the lower level of my home. Due to the floor being concrete under the ceramic tile there is a natural slant, or unevenness to the floor. My new vanity is about 1″ off on one front leg and about 1/2″ off on the other front leg.

The only solution I can think of to resolve this problem it is to build a small platform, but that seems extreme and may end up unsightly.

Screwing it into the wall will leave the appearance of a floating front on the vanity, so that won’t work. I have toyed with the idea of adding some wood under the front feet but that would leave the full side with a slanted appearance on the side (not the worst choice because it wouldn’t be very visible).

Anyway, I was wondering if you had any ideas for me to try. My wife was SOOO excited to see the remodeled bathroom…then I installed the bathroom vanity. Please help! Matthew

Answer: Matthew, I can relate. Uneven concrete floors are a common problem for remodelers and contractors. To prevent the type of situation you currently find yourself in, contractors frequently level the floor prior to installing flooring. They use either a self leveling compound in some cases, such as when installing a ceramic tile floor, or they literally build up a subfloor when the floor unevenness is as great as your situation.

In your particular case there are only a few possible solutions that I can suggest to you.

Installing a bathroom vanity on an uneven concrete floor.

First, as you suggested you could build a small platform to install the bathroom vanity on. This is not the worst of situations and if done tastefully, using fancy molding for example, it could look rather nice.

The second idea that comes to mind is to cut off a portion of the backside of the bathroom vanity along the base of it, such that is follows the contour of the uneven concrete floor. This would bring the feet down to the level of the floor on the front. Typically bathroom vanities have 2-3 inches of material that sits below the base shelf inside the vanity, so you should have enough clearance to trim the back base of the vanity. The process of adjusting and cutting material to be even with a slanted floor or any other uneven surface is referred to as scribing. Typically a compass is used for scribing very uneven surfaces, however in your case you should be able to get away with using a level.

To scribe the backside of the bottom of your bathroom vanity, so that you account for the unevenness of the floor, first find a helper. Next hold one end of a level on the high side of the floor and raise the far end up until the bubble is centered on the level. Also hold a string along the length of the level so that it extends out to the end of where the vanity would sit along the back wall. Have your helper hold the far end of the string so that it runs along the surface of the level and have the person measure the height from the concrete floor to the height of the string. This will tell you more accurately how uneven your floor is.

Next, transfer this height to the side of the bathroom vanity where you were holding the level and string (the high side of the concrete floor).

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Assuming there is a constant slope to the floor along the length of the vanity, scribe a horizontal line along the length of the vanity base that goes from the high point that you marked on one side of the vanity to the very bottom edge of the vanity base on the far side. You will also need to make the same scribe mark on the front side of the rear portion of the vanity. Also mark a line between the two points where you were holding the level and string. Now you can cut along these three lines to effectively remove a wedge of material from the back base of the vanity. Once you have completed these cuts, the bathroom vanity should sit level on the floor and look as if the bathroom vanity base and front legs merge into the rising concrete floor.

The third idea I can suggest only works if the bathroom vanity has a complete box footprint, verses legs, which unfortunately sounds to be your situation. You can shim the vanity such that it is level on the concrete floor, and then add some baseboard molding around the vanity to hide the shims.

Again, you will have to do the same type of scribing on the baseboard trim, however there is a lot less financial risk if you make a mistake on a piece of baseboard trim, just the cost of replacing a new trim board. Cutting a piece of baseboard trim is also much easier to do.

In addition, if the concrete floor is uneven from side to side and back to back, scribing the vanity could be a very complicated endeavor.

Good luck with your bathroom vanity, and I am sure one of these solutions will work for your wife.

For help on your bathroom remodeling project, see my Bathroom Remodeling Bid Sheet. The Bathroom Remodeling Bid Sheet provides a request for quote checklist section that you can provide to prospective bathroom remodeling contractors. It also includes a comprehensive bathroom remodeling cost breakdown table, in Microsoft Excel format, that allows the contractor to include his projected remodeling costs for every phase of the project.

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